Make creating RequestInfo backwards compatible with 3.10

It was unexpected that this object was being created directly
outside of aiohttp internals. While it looks like its only
used for mocking downstream, we can accomodate that by subclassing
the NamedTuple and providing a `__new__` while keeping the faster
`tuple.__new__` internally.

fixes #9866

aiohttp/client_reqrep.py

@@ -43,6 +43,7 @@
 from .formdata import FormData
 from .hdrs import CONTENT_TYPE
 from .helpers import (
+    _SENTINEL,
     BaseTimerContext,
     BasicAuth,
     HeadersMixin,
@@ -104,13 +105,27 @@ class ContentDisposition:
     filename: Optional[str]
 
 
-class RequestInfo(NamedTuple):
+class _RequestInfo(NamedTuple):
     url: URL
     method: str
     headers: "CIMultiDictProxy[str]"
     real_url: URL
 
 
+class RequestInfo(_RequestInfo):
+
+    def __new__(
+        cls,
+        url: URL,
+        method: str,
+        headers: "CIMultiDictProxy[str]",
+        real_url: URL = _SENTINEL,
+    ) -> "RequestInfo":
+        return tuple.__new__(
+            cls, (url, method, headers, url if real_url is _SENTINEL else real_url)
+        )
+
+
 class Fingerprint:
     HASHFUNC_BY_DIGESTLEN = {
         16: md5,

tests/test_client_request.py

@@ -1544,3 +1544,31 @@ async def test_connection_key_without_proxy() -> None:
     )
     assert req.connection_key.proxy_headers_hash is None
     await req.close()
+
+
+def test_request_info_back_compat() -> None:
+    """Test RequestInfo can be created without real_url."""
+    url = URL("http://example.com")
+    other_url = URL("http://example.org")
+    assert (
+        aiohttp.RequestInfo(url=url, method="GET", headers=CIMultiDict()).real_url
+        is url
+    )
+    assert aiohttp.RequestInfo(url, "GET", CIMultiDict()).real_url is url
+    assert aiohttp.RequestInfo(url, "GET", CIMultiDict(), real_url=url).real_url is url
+    assert (
+        aiohttp.RequestInfo(url, "GET", CIMultiDict(), real_url=other_url).real_url
+        is other_url
+    )
+
+
+def test_request_info_tuple_new() -> None:
+    """Test RequestInfo must be created with real_url using tuple.__new__."""
+    url = URL("http://example.com")
+    with pytest.raises(IndexError):
+        tuple.__new__(aiohttp.RequestInfo, (url, "GET", CIMultiDict())).real_url
+
+    assert (
+        tuple.__new__(aiohttp.RequestInfo, (url, "GET", CIMultiDict(), url)).real_url
+        is url
+    )